package filter.response;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class ImgeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //让浏览器3秒刷新
        resp.setHeader("refresh","3");
        //在内存中创建一个图片
        BufferedImage image=new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
        //创建一个画笔
        Graphics2D g =(Graphics2D) image.getGraphics();
        //设置背景颜色
        g.setColor(Color.white);    //白
        //从哪开始填充
        g.fillRect(0,0,80,20);

        /*给图片写数据*/
        //设置数据的背景颜色
        g.setColor(Color.orange);
        g.setFont(new Font(null,Font.ITALIC,20));
        //设置数据，显示位置
        g.drawString(MakeNull(),0,20);
        //告诉浏览器，这个请求用图片的方式打开
        resp.setContentType("image/jpeg");
        //网站存在缓存，不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");

        ImageIO.write(image,"jpg",resp.getOutputStream());
    }

    private String MakeNull()
    {
        //生成随机数
        Random random=new Random();
        String num=random.nextInt(9999999)+"";
        StringBuffer sb=new StringBuffer();
        for (int i = 0; i < 7-num.length(); i++) {
            sb.append("0");
        }
        num=sb.toString()+num;
        return num;
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}
